Ossification of iliolumbar ligament in ankylosing spondylitis

Case contributed by Dr Domenico Nicoletti


Ankylosing spondylitis for 17 years with history of chronic low back and neck pain and markedly reduced mobility in the cervical and lumbar region. He has always been and remains HLA-B27 negative; 10 years ago he developed Crohn’s disease, which has been controlled with sulfasalazine.

Patient Data

Age: 65
Gender: Male

Bilateral ossification of the iliolumbar ligament from the transverse process of the fifth lumbar vertebra to the iliac crest. The enlarged left L5 transverse process forming a pseudo-articulation with the iliolumbar ligament calcified. Sacroiliac joints are fused. Bamboo shaped spine due to syndesmophyte formation laterally. Interspinous/supraspinous ligamentous calcification (dagger sign).

Bilateral calcification of iliolumbar ligament with pseudo-articulation on the left side.

Squared-off configuration of vertebral bodies due to paraspinous ligamentous ossification along anterior vertebral body margins and syndesmophyte formation along anterior disc margins.

Rheumatology report                

Ankylosing spondylitis with normal phlogosis indices

Case Discussion

The iliolumbar ligament is a biomechanically important ligament in the lumbopelvic region. It functions to maintain the alignment of L5 on the sacrum during movement; it extends from the transverse processes of the 4th and 5th lumbar vertebrae to the iliac crest. The possible causes of ligament iliolumbar calcification or ossification include:

  1. Hypoparathyroidism.
  2. Ankylosing spondylitis - seropositive inflammatory spondyloarthropathies in general.
  3. Idiopathic skeletal hyperostosis – DISH.
  4. Degenerative diseases.
  5. Normal variation.

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